The main bridge of Jiangjin Zhongdu Changjiang River Bridge in Chongqing is a steel box girder suspension bridge with a main span of 600 m.The bridge is located in the upper reaches of the Changjiang River.The shoal area where the north-bank main span is located is a cultural relics protection zone for the lotus stones, therefore, blasting and excavation is forbidden in the construction.The steel box girder in the spans crossing the shoal area comprises of 22 sections, which are not able to be delivered punctually by barges in the low-water period of the river.Four delivery options were compared and analyzed from aspects of construction complexity, influence on environment and economic performance, including the scheme of using the cofferdam to store water, installing floating air bags under the delivery barges, using the floating cranes to deliver the girder section and using the tug boats to deliver girder sections.The scheme of using the tugboats to deliver steel sections was chosen.During the construction, the delivery boats transported the steel box girder sections to the cable cranes on the south bank, and batched there.The cable cranes then undertook the task of lifting the girder sections and then left the delivery boats.The tugboats drove the small barges to the cable cranes on the south bank to transfer the girder sections onto the small barges.Then, the tugboats drove the small barges forward following the chosen voyage line, to deliver the steel box girder sections to the cable cranes on the north bank for installation.%重庆市江津中渡长江大桥主桥为主跨600 m钢箱梁悬索桥,位于长江上游,北岸主跨浅滩区为莲花石实景保护文物,不能爆破及挖掘,北岸浅滩区钢箱梁共22个节段,在枯水期运输钢箱梁时不能保证运梁驳船按时供梁.对设置围堰蓄水方案、运输船底部设置浮运气囊方案、浮吊船转运方案和拖船转运方案进行对比分析,考虑施工难易程度、对环境影响、经济性等因素,确定钢箱梁采用拖船转运方案架设.施工时,运输船将北岸浅滩区钢箱梁运输至南岸缆载吊机正下方后进行抛锚定位,缆载吊机将待转运梁段提起,驶离钢箱梁运输船,拖船驱使小型驳船至南岸缆载吊机正下方将钢箱梁装于小型驳船上,拖船驱使小型驳船按照事先选择的航线行驶,将钢箱梁运输至北岸缆载吊机正下方进行起吊安装.
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